JPWO2016158552A1 - R-TM-B sintered magnet - Google Patents

Abstract

24.5-34.5 mass% R (R is at least one selected from rare earth elements including Y), 0.85-1.15 mass% B, less than 0.1 mass% Co, 0.07-0.5 mass% Ga, An R-TM-B sintered magnet containing 0 to 0.4 mass% Cu, unavoidable impurities, and the balance Fe, wherein the Ga and Cu contents are Ga content (mass%) and Cu content. On the XY plane with (mass%) as the X axis and Y axis respectively, point A (0.5, 0.0), point B (0.5, 0.4), point C (0.07, 0.4), point D (0.07, 0.1) and An R-TM-B sintered magnet characterized by being in a region surrounded by a pentagon having a point E (0.2, 0.0) as a vertex.

Description

  The present invention relates to an R-TM-B sintered magnet with improved corrosion resistance and an R-TM-B cylindrical anisotropic sintered magnet with reduced cracking.

  R-TM-B sintered magnets are widely used because of their high magnetic properties. However, the R-TM-B sintered magnet has a problem of being easily corroded because it contains a rare earth element (R element) as a main component. It is known that corrosion starts from a rare earth-rich phase containing a large amount of rare earth elements and proceeds while the main phase drops off. In order to prevent corrosion, the surface of R-TM-B sintered magnets is usually provided with a rust-preventive coating (painting or plating). It is difficult to prevent completely.

  As one of the forms of the R-TM-B sintered magnet, a cylindrical polar anisotropic magnet and a cylindrical radial anisotropic magnet are known. These cylindrical magnets are easy to assemble and widely used because they do not need to be attached to the rotor one by one like a bow-shaped magnet when used in a rotating machine.

  However, due to the anisotropy of these cylindrical magnets, there is a difference in the linear expansion coefficient between the C-axis direction of the magnet and the C-axis and the vertical direction, and the stress generated by the difference in these linear expansion coefficients is It becomes inherent in the cylindrical magnet. When this stress is greater than the mechanical strength of the cylindrical magnet, for example, as described in JP-A No. 64-27208, cracks and cracks occur. In the case of a block-shaped magnet, even if the linear expansion coefficients are different, the stress is released, so that the stress is not inherent in the magnet.

  Co is known as a metal that improves the corrosion resistance of R-TM-B sintered magnets. For example, JP-A-63-38555 describes that Co is taken into the main phase and grain boundaries of an R-TM-B sintered magnet to form an intermetallic compound with a rare earth element that is less susceptible to corrosion than a rare earth-rich phase. doing. On the other hand, however, the added Co is included not only in the main phase but also in the grain boundary phase, thereby causing a problem of reducing the mechanical strength. For this reason, R-TM-B sintered magnets containing Co are liable to be chipped and cracked during handling after sintering or grinding, which may reduce production efficiency.

  JP 2003-31409 describes the addition of Co and Cu to segregate Co and Cu around the R-rich phase (rare earth element-rich grain boundary phase) to form an intermediate phase, thereby converting the R-rich phase to Co. And a technique of coating with Cu to improve the corrosion resistance of individual R-rich phases. However, similar to Patent Document 2, there is a problem that the mechanical strength of the sintered magnet decreases due to the addition of Co. Therefore, it is desired to develop a technique for improving the corrosion resistance particularly in a magnet having a stress such as a cylindrical magnet. ing.

  Japanese Patent Laid-Open No. 2013-216965 discloses R, which is a rare earth element, T, which is a transition metal essential for Fe, a metallic element M containing one or more metals selected from Al, Ga, and Cu, and B And an alloy for RTB rare earth sintered magnets composed of inevitable impurities. However, no mention is made of techniques for improving corrosion resistance and strength, and there is no description of applying these R-T-B rare earth sintered magnet alloys to cylindrical magnets.

  As described above, in R-TM-B based sintered magnets, although corrosion resistance can be improved by adding Co, on the other hand, since mechanical strength is reduced, cylindrical polar anisotropy is particularly important. When applied to magnets and cylindrical radial anisotropic magnets, there is a problem that cracks, chips and cracks occur. Therefore, it is impossible to add a sufficient amount of Co to ensure corrosion resistance, or to ensure mechanical strength by increasing the size of the cylindrical magnet (the radial dimension of the cylindrical magnet). Sufficient attention was required for this.

  Accordingly, an object of the present invention is to provide an R-TM-B based sintered magnet that achieves both high mechanical strength and excellent corrosion resistance without adding Co.

  Another object of the present invention is to provide an R-TM-B cylindrical anisotropic sintered magnet with reduced generation of cracks, chips and cracks.

  As a result of diligent research in view of the above object, the present inventors have found that R-TM-B based sintered magnets added with Ga or (Ga + Cu) have excellent corrosion resistance even when they contain substantially no Co. The present invention finds that the occurrence of cracks, chips, cracks, etc. is reduced even when a cylindrical anisotropic sintered magnet that does not cause a decrease in mechanical strength and is liable to generate residual stress. I came up with it.

That is, the R-TM-B sintered magnet of the present invention is 24.5-34.5% by mass of R (R is at least one selected from rare earth elements including Y), 0.85-1.15% by mass of B, and 0.1 An R-TM-B based sintered magnet containing less than wt% Co, 0.07 to 0.5 wt% Ga, 0 to 0.4 wt% Cu, unavoidable impurities, and the balance Fe,
The content of Ga and Cu, Ga amount (mass%) and Cu amount (mass%) on the XY plane with the X axis and the Y axis, respectively, point A (0.5, 0.0), point B (0.5, 0.4 ), Point C (0.07, 0.4), point D (0.07, 0.1), and point E (0.2, 0.0).

  The R-TM-B sintered magnet of the present invention has 3 mass% or less of M (M is Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Ag, Mn, Ge , Sn, Bi, Pb and Zn) may be further contained.

  The Ga and Cu contents are Ga (mass%) and Cu (mass%) on the XY plane with the X axis and Y axis, respectively, point A (0.5, 0.0), point B (0.5, 0.4). ), Point C ′ (0.1, 0.4), point D ′ (0.1, 0.1), and point E (0.2, 0.0) are preferably in a region surrounded by a pentagon.

  The R-TM-B sintered magnet is preferably a cylindrical radial anisotropic magnet or a cylindrical polar anisotropic magnet.

  The R-TM-B sintered magnet of the present invention exhibits corrosion resistance by including Ga and Cu in a specific range instead of imparting corrosion resistance by containing Co. It is possible to achieve both excellent corrosion resistance. For this reason, it is possible to provide an R-TM-B sintered magnet with reduced occurrence of cracks, chips, cracks, etc., and cylindrical R-TM-B anisotropic sintering that is liable to generate residual stress. The present invention can also be applied to a binding magnet (cylindrical radial anisotropic magnet and cylindrical polar anisotropic magnet). Therefore, the R-TM-B based sintered magnet of the present invention can be preferably used as a magnet for a rotating machine.

It is a graph which shows the range of Cu amount and Ga amount which are contained in the R-TM-B system sintered magnet of the present invention. 4 is a SEM photograph showing the corrosion state of Alloy 1 (Ga / Cu = 0.1 / 0.02 mass%) after the pressure cooker test performed in Experimental Example 3. 4 is a SEM photograph showing a corrosion state of Alloy 4 (Ga / Cu = 0.5 / 0.4 mass%) after a pressure cooker test performed in Experimental Example 3. FIG. 6 is a schematic diagram showing a molding apparatus for molding the R-TM-B radial anisotropic ring magnet used in Experimental Example 4. 10 is a cross-sectional view schematically showing a molding apparatus for molding the R-TM-B polar anisotropic ring magnet used in Experimental Example 5. FIG. FIG. 5 is a cross-sectional view taken along line AA in FIG.

(1) Composition The R-TM-B based sintered magnet of the present invention comprises 24.5 to 34.5% by mass of R (R is at least one selected from rare earth elements including Y), and 0.85 to 1.15% by mass of B. R-TM-B sintered magnet containing less than 0.1% by mass of Co, 0.07 to 0.5% by mass of Ga, 0 to 0.4% by mass of Cu, unavoidable impurities, and the balance Fe,
The content of Ga and Cu, Ga amount (mass%) and Cu amount (mass%) on the XY plane with the X axis and the Y axis, respectively, point A (0.5, 0.0), point B (0.5, 0.4 ), Point C (0.07, 0.4), point D (0.07, 0.1), and point E (0.2, 0.0).

  The R-TM-B sintered magnet of the present invention preferably consists essentially of R-TM-B. Here, R is at least one of rare earth elements including Y, and preferably necessarily includes at least one of Nd, Dy, and Pr, and TM is at least one of transition metal elements, preferably Fe. . B is boron.

  The R-TM-B based sintered magnet has an R of 24.5-34.5% by mass. When the amount of R is less than 24.5% by mass, the residual magnetic flux density Br and the coercive force iHc decrease. If the amount of R exceeds 34.5% by mass, the rare earth-rich phase region inside the sintered body increases, so that the residual magnetic flux density Br decreases and the corrosion resistance decreases.

The R-TM-B sintered magnet has B of 0.85 to 1.15% by mass. When the amount of B is less than 0.85% by mass, B necessary for forming the main phase R ₂ Fe ₁₄ B phase is insufficient, and an R ₂ Fe ₁₇ phase having soft magnetic properties is generated and the coercive force is reduced. . On the other hand, when the amount of B exceeds 1.15% by mass, the phase rich in B which is a nonmagnetic phase increases and the residual magnetic flux density decreases.

  The R-TM-B sintered magnet contains 0.07 to 0.5% by mass of Ga. Ga has the effect of improving the corrosion resistance in addition to the effect of improving the coercive force. If it is 0.07% by mass or less, the effect of improving the coercive force iHc cannot be obtained. Even if Ga is added in an amount of more than 0.5% by mass, no further effect of improving the coercive force and improving the corrosion resistance cannot be expected. The effect of improving corrosion resistance due to the addition of Ga is sufficiently effective if contained in an amount of 0.07% by mass or more, but it is more preferable to contain 0.1% by mass or more. In particular, when Cu is not included, the Ga content is preferably 0.2% by mass or more.

  The R-TM-B based sintered magnet contains 0 to 0.4% by mass of Cu. Even if it does not contain Cu, the effect of the present invention can be obtained by adjusting the Ga content, but the corrosion resistance is further improved by containing Cu. When the Ga content is 0.07% by mass, it is preferable to contain 0.1% by mass or more of Cu. Even if Cu is added in an amount of more than 0.4% by mass, the effect of further improving corrosion resistance cannot be obtained.

  In the R-TM-B sintered magnet, in order to fully exhibit the effect of improving the corrosion resistance by Ga and Cu, the Ga content (Cu) and the Cu content (mass%) should be changed. On the XY plane as the X axis and Y axis respectively, point A (0.5, 0.0), point B (0.5, 0.4), point C (0.07, 0.4), point D (0.07, 0.1) and point E (0.2, 0.0) is set in the area surrounded by the pentagon. When the Ga and Cu contents are in this region, an R-TM-B sintered magnet having necessary magnetic properties and corrosion resistance can be obtained even when Co is not substantially contained. In the present invention, “substantially not containing” is indicated as “substantially” by allowing inclusion as an inevitable impurity.

  On the XY plane, the contents of Ga and Cu are point A (0.5, 0.0), point B (0.5, 0.4), point C ′ (0.1, 0.4), point D ′ (0.1, 0.1) and point E. It is preferably within a region surrounded by a pentagon with (0.2, 0.0) as the vertex, and point A (0.5, 0.0), point B (0.5, 0.4), point C "(0.2, 0.4) and point D" ( More preferably, it is in a region surrounded by a quadrangle with the vertices at 0.2, 0.1).

  Part of Fe may be substituted with Co, but if Co is contained in an amount of 0.1% by mass or more, cracking particularly occurs in cylindrical anisotropic sintered magnets, which is undesirable, so the Co content is It is preferably less than 0.1% by mass. In R-TM-B sintered magnets, Co may be used as a material that usually enhances corrosion resistance, but in the present invention, as described above, corrosion resistance can be imparted by Ga or Ga and Cu. The use of Co is not mandatory. However, 0.08 mass% or less of Co may be contained as an inevitable impurity of Fe. Although it is desirable that the amount of Co contained as an inevitable impurity is small, it is contained at a certain ratio depending on the purity of raw materials used in the mass production process and the addition of recycled materials. Co contained as an inevitable impurity is more preferably 0.06% by mass or less.

  One of the impurities that may be mixed into the R-TM-B sintered magnet from the raw material and its manufacturing process is Ni. Ni is known to be substituted for a part of Fe and to reduce the magnetic properties of R-TM-B magnets. In addition, inclusion of a certain amount or more of Ni is not desirable because cracks rapidly increase. Ni as an unavoidable impurity contained in the raw material and an impurity which is unintentionally mixed in the manufacturing process is preferably suppressed to less than 0.1% by mass, and more preferably 0.08% by mass or less.

R-TM-B based sintered magnets are further M (M is Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Ag, Mn, Ge, Sn, Bi, Pb and It may contain at least one selected from Zn. The addition of a small amount of metal element M changes the properties of the grain boundary phase, and the effect of improving the coercive force can be obtained.However, if added in a large amount, the volume ratio of the R ₂ Fe ₁₄ B phase decreases and Br decreases, so 3% It is preferable to keep it below.

(2) Magnet shape The R-TM-B sintered magnet of the present invention is preferably cylindrical. The cylindrical magnet preferably has radial anisotropy or polar anisotropy as an anisotropic direction. By adopting a cylindrical shape (ring shape), the number of assembling steps when assembling as a rotating machine can be reduced.

  The cylindrical magnet having the composition of the R-TM-B sintered magnet of the present invention has not only good corrosion resistance but also a very small amount even if it does not contain Co. There is no occurrence of cracks, chips, cracks, etc. due to it, or even if it occurs, the amount is extremely small.

  The R-T-B radial anisotropic ring magnet preferably has a ratio D1 / D2 between the inner diameter (D1) and the outer diameter (D2) of 0.7 or more.

  The number of poles when the R-T-B radial anisotropic ring magnet is multipolarized may be appropriately set according to the specification of the electric motor in which the magnet is used.

  The RTB polar anisotropic ring magnet has a ratio D1 / D2 between the inner diameter (D1) and outer diameter (D2) where the number of magnetic poles is P, the formula: D1 / D2 = 1-K (π / P ) [However, the value of K is 0.51 to 0.70 when P = 4, the value of K is 0.57 to 0.86 when P = 6, the value of K is 0.59 to 0.97 when P = 8, and the value of K is P = 10. The value is 0.59 to 1.07, the value of K is 0.61 to 1.18 when P = 12, and the value of K is 0.62 to 1.29 when P = 14. ] Is preferable.

  RTB polar anisotropy ring magnet is composed of 4 poles, 6 poles, 8 poles, 10 poles, 12 poles or 14 poles of multi-circular anisotropy and a circular cross section outer peripheral surface You may have. In that case, it is preferable that the number of poles of the outer peripheral surface is an integral multiple of the number of vertices of the polygon. Moreover, it is preferable that at least one of the intermediate positions of the pole positions of the outer peripheral surface and at least one vertex of a polygon of a cross section constituting the inner peripheral surface coincide with each other in the circumferential direction. The number of poles is preferably the same as or twice the number of vertices of the polygon. How to set the number of vertices of the polygon may be appropriately adjusted according to the number of poles. The polygon is preferably a regular polygon. In addition, when the cross section of an internal peripheral surface is a polygon, let the diameter of the circle | round | yen circumscribing a polygon be an internal diameter.

  The present invention will be described in more detail by the following experimental examples, but the present invention is not limited thereto.

Example 1
As shown in Table 1, Nd is 24.80% by mass, Pr is 6.90% by mass, Dy is 1.15% by mass, B is 0.96% by mass, Nb is 0.15% by mass, Al is 0.10% by mass, and Ga and Cu contents are shown in Table 1. Strip casting method of 25 types of alloys containing Fe and unavoidable impurities as the balance, with 0.1, 0.2, 0.3, 0.4, 0.5% by mass and 0.02, 0.1, 0.2, 0.3, 0.4% by mass, respectively. It was produced by. These alloys contained 0.06% by mass of Co as an inevitable impurity. The Cu content is a value containing 0.02% by mass of Cu contained as an inevitable impurity.

The resulting alloy is crushed by jet mill in nitrogen gas containing 5000 ppm oxygen, compression molded in a magnetic field, sintered and heat-treated, then ground, and R-TM-B sintered. A test piece of 3 mm × 10 mm × 40 mm made of a magnet was prepared. Using these test pieces, a pressure cooker test (120 ° C., 100% RH, 2 atm, 96 hours) was performed, and the weight loss (mg / cm ² ) was determined from the weight before and after the test. The results are shown in Table 1. These results are average values of the results of testing with n = 3 for each alloy.

  It can be seen that the addition of Ga or Ga + Cu reduces the corrosion weight loss of the R-TM-B sintered magnet and greatly improves the corrosion resistance. When Cu was not added (however, when 0.02% by mass of Cu was included as an inevitable impurity), the corrosion weight loss was remarkably large when the Ga content was 0.1% by mass, but when the Ga content was increased, the corrosion weight loss decreased and the corrosion resistance was reduced. Good results were obtained. When Cu was added at a Ga content of 0.1% by mass, the corrosion weight loss decreased and the corrosion resistance was improved.

If the corrosion weight loss is less than 2 mg / cm ² when the pressure cooker test is performed under the conditions of 120 ° C. 100% RH, 2 atm and 96 hours in the R-TM-B sintered magnet, It has been confirmed that it can satisfy the standards of corrosion resistance required for automobiles (electric equipment and HV).

  Therefore, the range of Cu and Ga content that is considered to be able to satisfy the above corrosion resistance standard even when substantially free of Co, Ga amount (mass%) and Cu amount (mass%) are respectively expressed in the X axis and Y direction. As shown in FIG. 1, on the XY plane as the axis, it can be seen that the region is surrounded by a pentagon with the point ABCDE as a vertex.

Experimental example 2
24.80% by mass of Nd, 6.90% by mass of Pr, 1.15% by mass of Dy, 0.96% by mass of B, 0.15% by mass of Nb, 0.10% by mass of Al, 0.30% by mass of Ga and 0.15% by mass of Cu, Alloy A containing Fe and inevitable impurities as the balance was prepared by strip casting. This alloy A contained 0.06% by mass of Co as an inevitable impurity.

  Alloys B to F were produced in the same manner as Alloy A except that the alloy composition was changed as shown in Table 2. Alloys A to E are included in the composition range of the R-TM-B sintered magnet of the present invention, and Alloy F is not included in the composition range of the R-TM-B sintered magnet of the present invention. Is.

Note (1) Co is an inevitable impurity.

The obtained alloys A to F were jet milled in nitrogen gas containing 5000 ppm oxygen, compression-molded in a magnetic field, sintered and heat-treated, then ground, and R-TM-B A test piece of 3 mm × 10 mm × 40 mm made of a sintered magnet was prepared. Using these test pieces, the remanence B _r and coercivity H _cJ measured, further pressure cooker test (120 ℃ 100% RH, 2 atm, 96 hours) performed, corrosion weight loss from the weight of before and after the test Asked. The results are shown in Table 3. The result of the pressure cooker test is an average value of the results of testing with n = 3 for each alloy.

Further, among the test pieces produced in Experimental Example 1, Ga content and Cu content are 0.1% by mass and 0.02% by mass of alloy 1, 0.1% by mass and 0.4% by mass of alloy 2, 0.5% by mass and 0.02% by mass, respectively. the% alloy 3 and 0.5 wt% and 0.4 wt% of the residual magnetic flux density B _r and the coercivity H _cJ of alloy 4 were measured. The results are shown in Table 3.

Alloy A~E and alloys 2-4 are included in the composition range of R-TM-B based sintered magnet of the present invention, the corrosion weight loss is small, it is found to have a high residual magnetic flux density B _r and the coercivity H _cJ . For alloy F, the sum of Nd, Pr, and Dy exceeds the rare earth amount specified in the present invention, and as a result, it is presumed that the corrosion resistance has deteriorated.

Experimental Example 3
About the alloy 1 with Ga content and Cu content of 0.1% by mass and 0.02% by mass obtained in Experimental Example 1, respectively, and the alloy 4 with Ga content and Cu content of 0.5% by mass and 0.4% by mass, respectively. A pressure cooker test was conducted under the conditions of 120 ° C., 100% RH, 2 atm and 24 hours, and the state of corrosion after the test was observed by SEM. The result is shown in figure 2.

  It was confirmed that the sample of alloy 1 (Fig. 2 (a)) was progressing in the depth direction (the part indicated by the arrow in the figure), but the sample of alloy 4 (Fig. 2 (b)) No progress of corrosion was confirmed.

Example 4
In order to evaluate the effect of Co content on the mechanical strength of R-TM-B sintered magnets, the following experiment was conducted.

  Nd 24.25% by mass, Pr 6.75% by mass, Dy 2.1% by mass, B 0.96% by mass, Nb 0.15% by mass, Al 0.06% by mass, Ga 0.08% by mass, Co content 0.0 The alloys were changed in the range of 0.06, 0.08, and 0.1 to 1.0% by mass (in increments of 0.1% by mass), and 13 kinds of alloys containing Fe and inevitable impurities as the balance were produced by strip casting. In the experiment, a high-purity metal was used, but a trace amount of inevitable impurities was included. Therefore, an alloy whose Co content is described as 0.0% by mass may actually contain Co below the measurement limit (0.01% by mass).

  The obtained alloy was crushed by jet mill in nitrogen gas containing 5000 ppm oxygen to prepare fine powder. Using the obtained fine powder, compression molding in a magnetic field (magnetic field strength: 318 kA / m, pressure: 98 MPa) using the molding equipment shown in Fig. 3 and molding of an R-TM-B radial anisotropic ring magnet (Outer diameter 41.8 mm × inner diameter 32.5 mm × height 47.2 mm) was obtained. Ten compacts were produced for each alloy.

  The molding equipment used to mold the R-TM-B radial anisotropic ring magnet includes cylindrical upper and lower cores 40a and 40b (made by permender), a cylindrical outer mold 30 (made by SK3), and a cylindrical shape. A die composed of upper and lower punches 90a and 90b (non-magnetic), a cavity 60 constituted by a space surrounded by these, and a pair of magnetic field generating coils respectively disposed at the outer peripheral positions of the upper core 40a and the lower core 40b It consists of 10a and 10b. The upper core 40a can be detached from the lower core 40b, the upper core 40a and the upper punch 90a can be moved up and down independently, and the upper punch 90a can be detached from the cavity 60. A magnetic field can be applied in the radial direction to the cavity 60 along the magnetic field line 70 through the closely contacted upper core 40a and lower core 40b.

Insert a sintering jig (material SUS403 linear expansion coefficient 11.4 × 10 ^-6 ) consisting of a cylindrical body with an outer diameter of 29.0 mm into the molded body, and place it on the Mo heat-resistant plate laid in the Mo container. It was sintered for 2 hours at 1080 ° C. in a vacuum. The sintering jig was used after applying Nd ₂ O ₃ stirred in an organic solvent to the outer peripheral surface. The end surface, outer peripheral surface and inner peripheral surface of the obtained sintered body were ground to produce 13 types of R-TM-B radial anisotropic ring magnets 401 to 413 having different Co contents. It was visually confirmed whether or not cracks occurred in the obtained R-TM-B radial anisotropic ring magnet. The results are shown in Table 4. The ring magnets 401 to 403 are reference examples in which the Ga content deviates from the present invention, but the Co content is less than 0.1% by mass (within the range specified in the present invention), and the ring magnets 404 to 413 have a Co content. Is 0.1% by mass or more (outside the range specified in the present invention).

  From the results of Table 4, it can be seen that when the Co content is 0.1% by mass or more, cracks occur in the sintered body of the ring magnet, and the occurrence of cracks increases as the Co content increases. .

Experimental Example 5
Using fine powders of 13 kinds of alloys prepared in the same manner as in Experimental Example 4, compression molding in a magnetic field (pressure: 80 MPa, magnetic field strength was the same under all conditions (pulse Thus, an R-TM-B polar anisotropic ring magnet molded body (outer diameter 31.5 mm × inner diameter 20.3 mm × height 27.8 mm) having eight poles on the outer peripheral surface was obtained. Ten compacts were produced for each alloy.

  As shown in FIG. 4 (a), the forming apparatus 100 in the magnetic field used for forming the R-TM-B polar anisotropic ring magnet has a die 101 made of a magnetic material and a concentric space in the annular space of the die 101. And a core 102 made of a cylindrical non-magnetic material, and the dice 101 are supported by support posts 111 and 112, and the core 102 and the support posts 111 and 112 are both supported by a lower frame 108. Similarly to the upper punch 104 made of a cylindrical non-magnetic material, the lower punch 107 made of a cylindrical non-magnetic material is fitted into the molding space 103 between the die 101 and the core 102, respectively. The lower punch 107 is fixed to the substrate 113, while the upper punch 104 is fixed to the upper frame 105. The upper frame 105 and the lower frame 108 are connected to the upper cylinder 106 and the lower cylinder 109, respectively.

  FIG. 4 (b) shows an AA cross section of FIG. 4 (a). A plurality of grooves 117 are formed on the inner surface of the cylindrical die 101, and a magnetic field generating coil 115 is embedded in each groove 117. An annular non-magnetic annular sleeve 116 is provided on the inner surface of the die 101 so as to cover the groove. A space 103 between the annular sleeve 116 and the core 102 is formed. In FIG. 4 (b), the magnetic field generating coil 115 in each groove 117 is arranged so that the current flows in a direction perpendicular to the paper surface, and the current direction of the coils adjacent in the circumferential direction is alternately reversed. So connected. When an electric current is passed through the magnetic field generating coil 115, a flow of magnetic flux as shown by an arrow A is generated in the forming space 103, and S, N in order in the circumferential direction at points where the magnetic flux hits the annular sleeve (start point and end point of the arrow) , S, N... And magnetic poles whose polarities alternate (eight poles in the figure) are formed.

  The obtained molded body was placed on a Mo heat-resistant plate laid in a Mo container and sintered at 1080 ° C. for 2 hours in a vacuum. The end face, outer peripheral face and inner peripheral face of the obtained sintered body were ground to produce 13 types of R-TM-B polar anisotropic ring magnets 501 to 513 having different Co contents. The obtained R-TM-B polar anisotropic ring magnet was visually checked for cracks. The results are shown in Table 5. The ring magnets 501 to 503 are reference examples in which the Ga content deviates from the present invention, but the Co content is less than 0.1% by mass (within the range defined by the present invention), and the ring magnets 504 to 513 have the Co content. Is 0.1% by mass or more (outside the range specified in the present invention).

  From the results of Table 5, it can be seen that when the Co content is 0.1% by mass or more, cracks occur in the sintered body of the ring magnet, and the occurrence of cracks increases as the Co content increases. .

Experimental Example 6
A radially anisotropic sintered ring magnet of the present invention example was manufactured in the same manner as in Experimental example 4 except that 25 kinds of fine alloy powders prepared in the same manner as in Experimental example 1 were used. As a result, all of these 25 types of radially anisotropic sintered ring magnets did not crack after grinding.

Experimental Example 7
A polar anisotropic sintered ring magnet of the example of the present invention was manufactured in the same manner as in Experimental Example 5 except that fine powders of 25 types of alloys prepared in the same manner as in Experimental Example 1 were used. As a result, all of these 25 types of radially anisotropic sintered ring magnets did not crack after grinding.

Claims (4)

24.5-34.5 mass% R (R is at least one selected from rare earth elements including Y), 0.85-1.15 mass% B, less than 0.1 mass% Co, 0.07-0.5 mass% Ga, An R-TM-B based sintered magnet containing 0 to 0.4% by mass of Cu, unavoidable impurities, and the balance Fe,
The content of Ga and Cu, Ga amount (mass%) and Cu amount (mass%) on the XY plane with the X axis and the Y axis, respectively, point A (0.5, 0.0), point B (0.5, 0.4 ), Point C (0.07, 0.4), point D (0.07, 0.1) and point E (0.2, 0.0) in the region surrounded by the pentagon with the apex at the point, R-TM-B system sintering magnet. In the R-TM-B sintered magnet according to claim 1,
3% by mass or less M (M is at least one selected from Zr, Nb, Hf, Ta, W, Mo, Al, Si, V, Cr, Ti, Ag, Mn, Ge, Sn, Bi, Pb and Zn R-TM-B based sintered magnet characterized by further containing In the R-TM-B sintered magnet according to claim 1 or 2,
The content of Ga and Cu, Ga amount (mass%) and Cu amount (mass%) on the XY plane with the X axis and the Y axis, respectively, point A (0.5, 0.0), point B (0.5, 0.4 ), Point C ′ (0.1, 0.4), point D ′ (0.1, 0.1), and point E (0.2, 0.0) in the region surrounded by a pentagon with vertices, R-TM-B system Sintered magnet. In the R-TM-B based sintered magnet according to any one of claims 1 to 3,
The R-TM-B sintered magnet is characterized in that the R-TM-B sintered magnet is a cylindrical radial anisotropic magnet or a cylindrical polar anisotropic magnet.